1. Field of the Invention
The present invention relates to a coasting or freewheel mechanism for use in a bicycle, and more particularly to a light weight and low cost coasting mechanism.
2. Description of Related Art
A bicycle uses a coasting mechanism, sometimes called a freewheel mechanism, to alternately link and detach the driving force of the pedals and the rear wheel of the bicycle. Many years ago, the pedals and the rear wheel were directly linked, so that the pedals rotated whenever the wheel turned. However, it was found to be desirable to include a mechanism which permits the bicycle to “coast”, i.e., to have the wheel turn without the pedals turning. This coasting action has traditionally been accomplished through the use of pawls and ratchet teeth which are held in close coaxial alignment by steel ball bearings. Bushings have also been tried, in place of ball bearings, but with limited success because of the requirement for both free running and close axial alignment for the ratchet pawls to work correctly. The steel rolling element bearings allow free running during coasting but must support the high force loads encountered during application of driving force. Bushings do not work well when contaminated and especially when using small clearances to hold coaxial alignment. Seals to prevent contamination also introduce excessive drag, but inadequate seals allow contamination with increased wear and drag. Through time, the rolling element steel ball bearings have been accepted as the best current solution. The drawbacks to the steel ball bearings are the weight and the cost, as well as the size constraints of fitting these bearings into the available space to meet the prevailing industry standards for the mating parts.
There remains a need for a coasting mechanism that is free running, like the steel ball bearing system, does not transfer the high force loads generated during application of driving force through the ball bearings but, rather, acts like the bushing systems during driving by transferring the loads directly, when no free rotation is required. It is also desirable that the cost of the coasting mechanism be as low as possible and that the mechanism be as light weight as possible, while still being sturdy and reliable. Certainly, to be accepted, this needed mechanism must be lower cost and/or lighter weight than the current alternatives in the marketplace. The present invention is a coasting mechanism which includes these and other important features.